Hard Cider Tip #14: pH and Acid

Are pH and acid the same? Is one more important than the other? Why should you even care? For the craft home hard cider maker, your pH is the most important of the two measurements. That’s because it lets you know whether your juice and cider are more susceptible to spoilage. Bacteria won’t live well in acidic solutions. Also, if you use sulfites, it’s critical to know your pH so you can dose the proper amount. Total acid on the other hand gives you an indicator of how acidic your hard cider will taste. A hard cider with high total acids will be harsher to drink the drier it is and the less tannins it has. Understanding the total acids allows you to develop better blends and figure out how to best use the apples or juice you have available.

At a basic level, pH is about making sure your juice is safe to ferment without risk of spoilage. Let’s take a specific example. I love Ambrosia apples. They are a great eating apple with medium sugar, low acid, no tannins, but a huge amount of aroma and crunch. I consider them a modern “Sweet” cider apple. I’d love to make a single variety hard cider from it but the pH is too high. It’s usually above 4, which tells me to blend it with something that has more acids to lower the pH. Ambrosia contributes to the hard cider by adding sugar and aromas but needs to be blended with something to lower the pH and add a touch more acid. I often choose GoldRush which has a lower pH and around 8-10 grams per liter of malic acid versus the 3-5 found in Ambrosia apples.

Understanding the total acid will give you insights into your apples or your juice and how to make a balanced cider. Balanced hard ciders are what you want to make great hard ciders. I also make drier hard ciders so it’s important for me to understand my total acid level so I can decide how to bring it into balance or accentuate it. So how do you measure total acid? You have to titrate your juice or cider. You can buy or make your titration kit. I modified the standard kit shown on my recommended products page by adding 1ml and 3ml syringe and a small 10ml graduated cylinder. Here is what mine looks like.

Titration Kit
Titration Kit

Basically, acid titration is a process where you mix an indicator solution, phenolphthalein, into a specific amount of juice or cider. Next, you mix in a known reagent, NaOH 0.2N, until the juice with the indicator solution permanently changes colors. The amount of reagent you add to achieve the color change, defines the amount of acid in the juice. Since I am assessing apples, the method I use defines the total acid in terms of grams per liter of malic acid. As I previously said, this is different from pH. To measure pH, I recommend a meter. They are not that expensive and much more accurate than the pH test strips that change color.

pH Meter
pH Meter

The pH of a solution assesses the amount of free hydrogen ions in a solution. In strong acids, this does correspond to the total acids, but acids like malic, lactic, critic, tartaric, and acetic are weak acids so you can’t accurately correlate pH and total acid. Free hydrogen ions want to attach themselves to other ions, which breakdown the material in which they are in contact. This is the corrosion we associate with acids. In Claude Jolicoeur’s book, The New Cider Maker’s Handbook, he shows a plot of data that has been collected for apple juice comparing pH and total acid. That data says that apple juice with a pH of 3.5 could have a total acid measurement from 3 to 10.5 grams per liter. I have personally found this to be true. That is a huge difference if you are trying to create a balanced hard cider. An apple with a pH of 3.5 can easily be fermented as a single variety, but it would have a significantly different taste with 3 grams per liter of total acid versus 10.5.

Interestingly, there are ways to reduce the total acids in your hard cider. Yeast can convert stronger acids into weaker acids. Many hard ciders go through malolactic fermentation (MLF) during aging where malic acid is converted to softer or weaker lactic acid. You can also pitch or inoculate your juice with a commercial yeast strain that will convert malic acid into a weaker acid. Lalvin 71B™ is an example of this type of yeast. If you know you have a juice that is high in total acid, these are ways to proactively work to reduce it.

For actual examples, I have found Granny Smith apples can easily have 13-14 g/l while a Mutsu might have 4-5g/l. A Mutsu might have a pH of 3.6 and a Granny Smith 3.4. Both could be fermented without too much risk of spoilage but the Granny will be a much more acidic hard cider if fermented dry as a single variety hard cider. It’s why I tend to blend it and use it for berry ciders. Understanding your apples helps you make better hard cider. And, understanding your apples means understanding your pH and your total acid. Here is an example of the data I track. I’ve included my entire apple database in my book.

Traditional Hard Ciders
Apple Database: Tracking Apple data for hard cider.

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